OBSERVATIONS AND MODEL COMPARISONS OF EARLY-TIME EXPANSION CHARACTERISTICS OF A SATELLITE-BORNE BARIUM-LITHIUM RELEASE AT F-REGION ALTITUDES

We describe the very-early-time expansion processes (almost-equal-to 0 - 3 s) of the CRRES G-9 Ba+/Li+ cloud release, as manifested by therm al- and photo-ionization mechanisms, by coupling to the background ion osphere, and by differential acceleration of multi-ion constituents. I n our data analysis we present the very first ''in situ'' evidence of electrostatic snowplow effects in an expanding plasma cloud, with argu ments that these effects are the result of ambipolar fields and that k inetic effects of ion-neutral collisions have little influence in the G-9 scenario. In addition to the electrostatic snowplow process, the r esults show mass-dependent effects on the expansion of ion and neutral constituents in the cloud. These effects are manifested in the observ ation that the Li+ ions ''outpace'' the heavier Ba+ in the expansion p rocess, and take on forerunner characteristics at the cloud's leading edge.